Optical modulator, light source module, optical engine, and XR glasses

An optical modulator, which is a Mach-Zehnder-type optical modulator comprising:

• a substrate;
• and an optical waveguide layer including a lithium niobate film formed on the substrate,
• wherein the optical waveguide layer includes a plurality of flat portions and n ridge portions arranged between the flat portions to be adjacent, where n is an integer of two or more,
• wherein each of the n ridge portions includes a main waveguide to which a visible light beam is input, a first multimode interference waveguide through which the main waveguide is branched into a first optical branch waveguide and a second optical branch waveguide, and a second multimode interference waveguide through which the first optical branch waveguide and the second optical branch waveguide are coupled to form a coupling waveguide,
• wherein the visible light beams have different wavelengths and are input to the n ridge portions,
• wherein, for any two of the n ridge portions, the first and second multimode interference waveguides with shorter lengths are designed for the input visible light beam having the longer wavelength,
• wherein the n ridge portions include a first ridge portion and a second ridge portion, the first ridge portion includes first and second multimode interference waveguides having a first length and the second ridge portion includes first and second multimode interference waveguides having a second length shorter than the first length, and the second ridge portion is configured for visible light having a longer wavelength than the first ridge portion, and
• wherein the optical modulator further comprises a waveguide circuit to which at least two of the coupling waveguides of the n ridge portions are coupled on the substrate to form an output waveguide, wherein the waveguide circuit includes at least one multimode interference waveguide configured to couple the at least two of the coupling waveguides.